The use of signal lighting is known in the art. WO2009042252, for instance, describes an LED signal lamp comprising a housing, at least one LED excitation source operable to emit excitation radiation of a first wavelength range (blue light), at least one phosphor material for converting at least a part of the excitation radiation to radiation of a second wavelength range and a substantially transparent cover provided on the housing opening. In one arrangement the excitation source (LED chip) incorporates the phosphor material. Alternatively, the phosphor can be provided remote to the excitation source such as for example on a transparent substrate which is disposed between the excitation source and transparent cover. In other arrangements of WO2009042252, the phosphor is provided on the transparent cover. In yet other arrangements, the phosphor is provided on the transparent cover of other special optical components as a layer on a surface of the cover or incorporated within the cover/optical component material.
WO2007125493 describes a light-emitting device, comprising at least one light-emitting diode for emitting light of a first color and a luminescent material arranged on said at least one light-emitting diode to receive at least part of the light emitted by said light-emitting diode. The light-emitting device further comprises a filter arranged to receive light emitted by said light-emitting diode and transmitted through said luminescent material and to absorb light of said first color. The filter comprises a pigment compound distributed in a matrix of silicon and oxygen atoms, in which matrix at least a portion of said silicon atoms are directly bonded to hydrocarbon groups.
EP2736086 describes a semiconductor device, and a light emitting device package usable with a lighting apparatus is disclosed. The light emitting device package comprises a package body, a light emitting device located on the package body, the light emitting device emitting light having a first wavelength band, a transparent substrate located over the light emitting device with a distance therebetween, a wavelength conversion layer located on the transparent substrate, wherein the wavelength conversion layer absorbs and converts at least a part of the light having the first wavelength band into light having a second wavelength band, and a color calibration layer located on the wavelength conversion layer, the color calibration layer calibrating color of the wavelength conversion layer.
U.S. Pat. No. 5,277,841 describes a mixed blue emitting phosphor which is obtained by mixing ZnS:Ag,Al with at least one green emitting phosphor selected from the group consisting of Y3(Al,Ga)5O12:Tb, Y2SiO5:Tb and LaOCl:Tb of an amount below 20 wt. %, thereby greatly enhancing luminance and luminance-saturation characteristic.
US2011291132 describes a light-emitting device (LED). The LED includes a carrier substrate having a blue light emitter thereon. A layer containing a fluorescent material is on the blue light emitter. An encapsulant is disposed around the blue light emitter. Pigments are suspended between an outer surface of the encapsulant and the blue light emitter.
US2009167151 describes a lighting device, a backlighting device, and a display device that comprise a radiation source such as LED and wavelength converting members comprising phosphors. In one embodiment, self-absorption within the devices is suppressed or reduced by placing a selective reflector between two wavelength converting members, and the wavelength converting member emitting light with longer peak wavelength is substantially isolated from the irradiation of another wavelength converting member emitting light with shorter peak wavelength. In other embodiments, the wavelength converting members are arranged in strip configuration; or in adjacent hexagons configuration.